By Mark Petrie, Ph.D.
Waterfowl migration habits, food preferences, and courtship activities can all have an impact on hunting success.
Most of us recognize that there are patterns to waterfowl behavior over the course of a hunting season. Opening-day birds are more trusting than their late-season counterparts, ducks seem more willing to decoy after a midseason cold front, and some species are more easily deceived than others. Many of our hunting tactics have evolved in response to these behaviors; you could fill a library with articles on how to fool a January duck. Although hunting pressure undoubtedly alters bird behavior, waterfowl were avoiding predators and searching for their next meal thousands of years before anybody picked up a gun. How a duck responds to our decoys is partly the result of evolutionary forces that have shaped waterfowl behavior for millennia and now influence their vulnerability to hunting.
Your average decoy spread is trying to communicate several messages to a passing duck. First, this is a place of safety. Not only is it safe, but there is food here as well. And if you need a mate, well there's a singles dance happening right this minute. A false sense of security, food, and social opportunity is what those plastic cheats are peddling. Whether a bird buys the facade partly depends on its willingness to take risks. For each species, that is influenced by its life-history strategy.
Shorter-lived species tend to produce more young in a single year than do longer-lived species because they have fewer opportunities to breed. For example, American green-winged teal have a lower annual survival rate than northern pintails but are more productive on the breeding grounds. If your average teal has a single shot at immortality, he or she may be more willing to take the risks associated with finding a mate or acquiring the body fat reserves necessary for reproduction. To test this theory, waterfowl researchers in California ranked several species of dabbling ducks based on their average lifespan and annual reproductive output. They then determined the willingness of each species to approach decoys. As predicted, the shorter-lived and more-productive species like cinnamon and green-winged teal decoyed more readily than did longer-lived and less-productive species like pintails and mallards.
Although a species' life history may influence its eagerness to decoy, other factors like food are also important. Consider diving ducks. Their food is often found well below the surface, where it can't be seen. Consequently, divers rely heavily on the presence of other ducks as a cue to where they can find their next meal, which might explain why divers often decoy with abandon. In contrast, dabbling ducks can likely evaluate many foraging opportunities on the wing based on wetland vegetation or even crop types. If your decoys aren't sitting on what dabblers perceive to be groceries, you may be out of luck.
As all hunters know, members of the same waterfowl species often react very differently to the same set of decoys. The evolutionary forces that balance risk against future reproduction are at play here too. A single late-season drake mallard that responds to a call is engaging in this math. He's well-schooled in danger, but the window to find a mate is closing. His willingness to join your decoys for social reasons may be growing despite his unease. Contrast that with paired mallards that can be notoriously difficult to decoy after New Year's Day. Many of these pairs want to be alone and away from the very social scene you've created.
How a bird's behavior changes during the hunting season also takes us into the murky world of how ducks learn and how they apply that knowledge to avoid hunters. Ducklings imprint on their mother almost immediately after hatching, proving that the birds are quick learners. However, a recent study published in Science also suggests that ducks are capable of abstract thought, a trait we usually associate with highly intelligent animals like canines and primates. One of the hallmarks of abstract thinking is the ability to compare different situations and recognize common elements among them.
Waterfowl that spend time in heavily hunted areas may engage in two types of "thinking." The first is purely literal and focused on the physical world, in what sociologists would call concrete thought. For example, when a drake mallard is shot at over a distinct point of land, he immediately associates that exact location with danger and may never cross it again. As the season progresses, he has similar encounters in a marsh, a rice field, and flooded timber. While these habitats are very different, our bird recognizes other common elements in each of these brushes with danger. Other ducks were present but strangely still, and hunters suddenly appeared from a partially concealed, geometrically shaped area rarely seen in nature. Based on these experiences, our mallard may learn to recognize and avoid decoys and blinds in other locations. That's an example of abstract thought.
Waterfowl often find themselves in unfamiliar areas because of their migratory nature, so the evolution of abstract thinking makes sense. If you are frequently going from one new area to the next, it helps to recognize the elements of danger that are common to all areas. The balance between concrete and abstract thinking may also help explain why hunting often picks up after a cold front delivers new birds. Research suggests that newly arrived ducks evaluate their surroundings for certain landscape characteristics, such as wetland abundance, before settling down within a smaller geographic area. Although this kind of exploration makes perfect sense, it also increases a bird's vulnerability to hunting.
Recent migrants are unfamiliar with local points of danger, and concrete thinking alone may not be enough to keep them safe. Moreover, the birds are likely to be hungry after a long flight, tilting the risk-reward equation in favor of your decoys. The ability to engage in abstract thought, and to recognize universal elements of danger, may be disproportionately important for waterfowl during those first few days. As the birds acquire local knowledge of their new home, both kinds of thought may become fully engaged. These are your "stale" birds that can be notoriously difficult to decoy, and ingenious hunting techniques or severe weather may be required to temporarily lower their defenses.
This story ends where it must, with the northern shoveler. Who hasn't pondered why spoonbills toll to decoys when other ducks refuse? I put this question to two unapologetic shoveler hunters. They claimed that even spoonies become decoy-shy if you hunt them hard enough. Apparently, they are capable of concrete and abstract thought just like other ducks. Interestingly, shovelers ranked just behind teal in their willingness to decoy in the California study. Maybe they are just naturally disposed to roll the dice, or like diving ducks, they may rely more on the presence of other birds to find food. We may never know the reason why some birds respond to our decoys and calling and others do not. That's all part of the mystery of waterfowl, and that's what makes waterfowl hunting such a challenging and fascinating pursuit.
Dr. Mark Petrie is director of conservation planning in DU's Western Region.